Make the "unref" operation on database pages a method which is part of the

PgHdr object.  This is a potential performance optimization.

FossilOrigin-Name: 37c5c8aa0ed93a39169f26297c4c145224e7f612260aed010c2e6add5a99d03d

manifest

@@ -1,5 +1,5 @@
-C Minor\sperformance\soptimization\sin\sthe\scomputation\sof\san\saffinity\sstring\nfor\san\sindex.
-D 2023-02-27T18:55:37.933
+C Make\sthe\s"unref"\soperation\son\sdatabase\spages\sa\smethod\swhich\sis\spart\sof\sthe\nPgHdr\sobject.\s\sThis\sis\sa\spotential\sperformance\soptimization.
+D 2023-02-27T21:53:44.955
 F .fossil-settings/empty-dirs dbb81e8fc0401ac46a1491ab34a7f2c7c0452f2f06b54ebb845d024ca8283ef1
 F .fossil-settings/ignore-glob 35175cdfcf539b2318cb04a9901442804be81cd677d8b889fcc9149c21f239ea
 F LICENSE.md df5091916dbb40e6e9686186587125e1b2ff51f022cc334e886c19a0e9982724
@@ -609,11 +609,11 @@ F src/os_setup.h 6011ad7af5db4e05155f385eb3a9b4470688de6f65d6166b8956e58a3d87210
 F src/os_unix.c 90c4fa0a88c8b0817c7ce4dbea0ac3aebfd7deb0797945ac34dfd25006ba393a
 F src/os_win.c 295fe45f18bd86f2477f4cd79f3377c6f883ceb941b1f46808665c73747f2345
 F src/os_win.h 7b073010f1451abe501be30d12f6bc599824944a
-F src/pager.c 39af8ff7c73a991f61f4d1e3a6f8f98b1c8e29144723507822774cac5e6ee0b5
+F src/pager.c b056782430e5f93db75e884d91dde1fbbb56109c7a8c1d75b7dc1ef0f35440dd
 F src/pager.h f82e9844166e1585f5786837ddc7709966138ced17f568c16af7ccf946c2baa3
 F src/parse.y 960d2da92a23f8ba2ca22748a51bd75ee2c575564f2cbc59f119640e7f5b4c5d
 F src/pcache.c f4268f7f73c6a3db12ce22fd25bc68dc42315d19599414ab1207d7cf32f79197
-F src/pcache.h 4f87acd914cef5016fae3030343540d75f5b85a1877eed1a2a19b9f284248586
+F src/pcache.h 1ecc890f77edec796f6ab31c7bee576243a31d9ed1208ae06ff37cd7b3c89b77
 F src/pcache1.c dee95e3cd2b61e6512dc814c5ab76d5eb36f0bfc9441dbb4260fccc0d12bbddc
 F src/pragma.c 82d5090a35eac75876d3b41f48d06b2370553c9576bf2942233c462e03eb94c9
 F src/pragma.h e690a356c18e98414d2e870ea791c1be1545a714ba623719deb63f7f226d8bb7
@@ -2047,8 +2047,11 @@ F vsixtest/vsixtest.tcl 6a9a6ab600c25a91a7acc6293828957a386a8a93
 F vsixtest/vsixtest.vcxproj.data 2ed517e100c66dc455b492e1a33350c1b20fbcdc
 F vsixtest/vsixtest.vcxproj.filters 37e51ffedcdb064aad6ff33b6148725226cd608e
 F vsixtest/vsixtest_TemporaryKey.pfx e5b1b036facdb453873e7084e1cae9102ccc67a0
-P 18ee689de3d1ae43b05ca52e0b62c49442ebf68a88814a7c679e8856250a4b0d
-R eb05b938ae3801da35ea0ed3c7e2ba02
+P 07334aa17b6ded27c5bd353998d96645a94cdcf32440abb59d127a002cd98ce9
+R 884ad767d802c01a8177e09c501a4836
+T *branch * unref-opt
+T *sym-unref-opt *
+T -sym-trunk *
 U drh
-Z 906f03c389d933535de5a426ca60838f
+Z f513eba7828052324439b98223896c77
 # Remove this line to create a well-formed Fossil manifest.

manifest.uuid

@@ -1 +1 @@
-07334aa17b6ded27c5bd353998d96645a94cdcf32440abb59d127a002cd98ce9
+37c5c8aa0ed93a39169f26297c4c145224e7f612260aed010c2e6add5a99d03d

src/pager.c

@@ -3990,6 +3990,20 @@ static int pagerSyncHotJournal(Pager *pPager){
   return rc;
 }
 
+/*
+** Release a reference to page pPg. pPg must have been returned by an 
+** earlier call to pagerAcquireMapPage().
+*/
+static void pagerReleaseMapPage(PgHdr *pPg){
+  Pager *pPager = pPg->pPager;
+  pPager->nMmapOut--;
+  pPg->pDirty = pPager->pMmapFreelist;
+  pPager->pMmapFreelist = pPg;
+
+  assert( pPager->fd->pMethods->iVersion>=3 );
+  sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData);
+}
+
 #if SQLITE_MAX_MMAP_SIZE>0
 /*
 ** Obtain a reference to a memory mapped page object for page number pgno. 
@@ -4023,6 +4037,7 @@ static int pagerAcquireMapPage(
     }
     p->pExtra = (void *)&p[1];
     p->flags = PGHDR_MMAP;
+    p->xUnref = pagerReleaseMapPage;
     p->nRef = 1;
     p->pPager = pPager;
   }
@@ -4030,6 +4045,7 @@ static int pagerAcquireMapPage(
   assert( p->pExtra==(void *)&p[1] );
   assert( p->pPage==0 );
   assert( p->flags==PGHDR_MMAP );
+  assert( p->xUnref==pagerReleaseMapPage );
   assert( p->pPager==pPager );
   assert( p->nRef==1 );
 
@@ -4041,20 +4057,6 @@ static int pagerAcquireMapPage(
 }
 #endif
 
-/*
-** Release a reference to page pPg. pPg must have been returned by an 
-** earlier call to pagerAcquireMapPage().
-*/
-static void pagerReleaseMapPage(PgHdr *pPg){
-  Pager *pPager = pPg->pPager;
-  pPager->nMmapOut--;
-  pPg->pDirty = pPager->pMmapFreelist;
-  pPager->pMmapFreelist = pPg;
-
-  assert( pPager->fd->pMethods->iVersion>=3 );
-  sqlite3OsUnfetch(pPager->fd, (i64)(pPg->pgno-1)*pPager->pageSize, pPg->pData);
-}
-
 /*
 ** Free all PgHdr objects stored in the Pager.pMmapFreelist list.
 */
@@ -5517,6 +5519,7 @@ static int getPageNormal(
     }
 
     pPg->pPager = pPager;
+    pPg->xUnref = sqlite3PcacheRelease;
 
     assert( !isOpen(pPager->fd) || !MEMDB );
     if( !isOpen(pPager->fd) || pPager->dbSize<pgno || noContent ){
@@ -5698,12 +5701,9 @@ DbPage *sqlite3PagerLookup(Pager *pPager, Pgno pgno){
 void sqlite3PagerUnrefNotNull(DbPage *pPg){
   TESTONLY( Pager *pPager = pPg->pPager; )
   assert( pPg!=0 );
-  if( pPg->flags & PGHDR_MMAP ){
-    assert( pPg->pgno!=1 );  /* Page1 is never memory mapped */
-    pagerReleaseMapPage(pPg);
-  }else{
-    sqlite3PcacheRelease(pPg);
-  }
+  assert( (pPg->flags & PGHDR_MMAP)==0 || pPg->xUnref==pagerReleaseMapPage );
+  assert( (pPg->flags & PGHDR_MMAP)!=0 || pPg->xUnref==sqlite3PcacheRelease );
+  pPg->xUnref(pPg);
   /* Do not use this routine to release the last reference to page1 */
   assert( sqlite3PcacheRefCount(pPager->pPCache)>0 );
 }

src/pcache.h

@@ -29,6 +29,7 @@ struct PgHdr {
   PCache *pCache;                /* PRIVATE: Cache that owns this page */
   PgHdr *pDirty;                 /* Transient list of dirty sorted by pgno */
   Pager *pPager;                 /* The pager this page is part of */
+  void (*xUnref)(PgHdr*);        /* Release function */
   Pgno pgno;                     /* Page number for this page */
 #ifdef SQLITE_CHECK_PAGES
   u32 pageHash;                  /* Hash of page content */